In manufacturing of integrated circuits, display panels, disks and the like, sputtering (hereinafter also referred to as sputter) is widely used to form a film on a substrate such as a semiconductor wafer, a glass panel, and a resin disk. Sputter is a film formation technique in which ions collide with the surface of a target, and thereby particles are ejected from the surface and are deposited on a substrate to form a film. The target is fixed to a backing plate. The backing plate is cooled by a cooling means, thereby cooling the target. The backing plate also functions as an electrode that applies a voltage to the target.
In order to perform sputter efficiently, a magnetron sputter is widely used in which a magnet is disposed on the back surface of the target. In the magnetron sputter, a voltage is applied to a target to form plasma formed in an area near the target, and the plasma thus formed is confined to the area near the target by a magnetic field, so that the sputter can be performed efficiently. A configuration is proposed in which a shield enclosing the outer circumference of the target is grounded (hereinafter also referred to as ground shield) to serve as an anode whereas the target and the backing plate function as a cathode under application of a voltage (Patent Document 1). In addition, Patent Document 1 discloses that the shield is made of a magnetic material, thereby further confining the plasma to the area near the target.